jefg231 : If you could get me a measurement of the length and diameter, plus a shot looking straight at them I could help you narrow them down. My first thought is .50 BMG, but they look a bit small for that from your pic.
I wouldn't even try to guess exactly what they are without some very close measurements. All I can tell really is that they appear jacketed which would make their age sometime between about 1900 to present and that they are not muzzle loading bullets. Anyone who hunts for or collects bullets should invest in a cheap micrometer to take measurements. You can get a set at a store that sells handloading equipment for less than $30.00 that will be precise enough to help ID bullets. A micrometer comes in handy for many other types of measurements besides justs bullets. I am a handloader and couldn't get along without my set of mikes. Monty
There you go, good old Harbor Freight. I bought a few of their "metal detectors", otherwise known by detectorists as pin pointers and after over a year , they are still working and only cost about fifteen bucks. Monty